<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <!-- <style>
      /* 样式表 */
      .yellow {
        width: 500px;
        height: 300px;
        background-color: yellow;
      }
      #div {
        width: 500px;
        height: 300px;
        background-color: green;
      }
    </style> -->
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <!-- 内联样式 -->
    <div style="width: 500px; height: 300px; background-color: aqua"></div>
    <!-- 内部样式 -->
    <!-- 类选择器 -->
    <div class="yellow"></div>
    <!-- id选择器 (不能重名)-->
    <div id="div"></div>
  </body>
</html>
